Cardiopulmonary effects of xylazine sedation in the foal.

Six healthy foals underwent instrumentation for measurement of the cardiopulmonary effects of sedation with 1.1 mg/kg bodyweight xylazine hydrochloride given intravenously. Responses to xylazine in foals at 10 and 28 days of age were not significantly different. Foals became sedate and markedly ataxic, and four of the six foals became recumbent. Heart rate decreased significantly but no arrhythmias were detected. Arterial blood pressure increased initially and then fell significantly below pre-injection values. Changes in respiratory airflow, upper airway obstruction and respiratory noise were noted in the initial 20 mins of sedation, after which respiratory rate fell, tidal volume increased, and minute volume decreased gradually. Arterial blood gas tensions and pH did not change significantly during the 120 mins following xylazine administration. Control studies showed no significant changes. All foals recovered uneventfully.